Our Natural Protection Our Natural Protection Against UV light.Against UV light.

The Ozone layer that blocks out the sun’s harmful The Ozone layer that blocks out the sun’s harmful rays is being depleted.rays is being depleted.

Todd Olsen Todd Olsen Professor KimballProfessor KimballChem 1A 31193Chem 1A 31193

What is causing the Depletion What is causing the Depletion of the Earth’s natural defense of the Earth’s natural defense from the sun?from the sun?• Man-made compounds are responsible for Man-made compounds are responsible for

the destruction. The most common are the destruction. The most common are chlorofluorocarbons (CFC’s) and halons. chlorofluorocarbons (CFC’s) and halons. The halogens Chlorine, Bromine, and The halogens Chlorine, Bromine, and Fluorine are often found in these Fluorine are often found in these compounds. And when broken down to compounds. And when broken down to their elemental state are the cause of the their elemental state are the cause of the depletion. We will get to this later.depletion. We will get to this later.

• Chlorofluorocarbons are used for various Chlorofluorocarbons are used for various purposes by man:purposes by man:

What Is OzoneWhat Is Ozone

• Ozone is a gas that forms Ozone is a gas that forms from 3 oxygen atoms (O3). from 3 oxygen atoms (O3). It exists in 2 places in our It exists in 2 places in our atmosphere. The ground atmosphere. The ground level near the earth known level near the earth known as the troposphere. This as the troposphere. This O3 is responsible for smog O3 is responsible for smog in large cities and causes in large cities and causes harmful effects to us as harmful effects to us as well as plants and animals. well as plants and animals.

• Ozone exists above the Ozone exists above the Stratosphere and this O3 Stratosphere and this O3 protects us and the planet protects us and the planet from the sun’s ultraviolet from the sun’s ultraviolet rays (UV-b). rays (UV-b).

Uses of CFC’sUses of CFC’s

• These items that give These items that give comfort and ease to our comfort and ease to our everyday lives contain these everyday lives contain these ozone damaging compounds ozone damaging compounds which allow them to which allow them to operate. When CFC’s are operate. When CFC’s are released into the air after released into the air after use they travel through the use they travel through the atmosphere until they reach atmosphere until they reach the stratosphere where the the stratosphere where the sun breaks down the sun breaks down the molecules to their elemental molecules to their elemental state. It’s in this state that state. It’s in this state that the halogens, particularly Cl the halogens, particularly Cl and Br can damage the and Br can damage the Ozone layer. Ozone layer.

• These can take years to These can take years to reach this level of the reach this level of the atmosphere. 1 molecule of atmosphere. 1 molecule of Cl or Bromine can destroy Cl or Bromine can destroy many thousands of many thousands of molecules. They do so by molecules. They do so by reacting with O3 by reacting with O3 by catalytic cycles. Or to catalytic cycles. Or to make it more simple. A make it more simple. A number of reactions can number of reactions can occur.occur.

A simple reaction that A simple reaction that Damages O3 (Ozone)Damages O3 (Ozone)

• Cl + O3 --- ClO + O2.Cl + O3 --- ClO + O2.

• In this simple reaction Cl reacts and In this simple reaction Cl reacts and bonds with one of the oxygen atoms bonds with one of the oxygen atoms in O3 leaving behind just a normal in O3 leaving behind just a normal Oxygen O2 molecule.Oxygen O2 molecule.

This original Cl atom isn’t This original Cl atom isn’t done!done!• Suppose this ClO atom that we have from Suppose this ClO atom that we have from

the last reaction is still floating around the last reaction is still floating around above the stratosphere. It meets up with a above the stratosphere. It meets up with a lone O atom and forms a new reaction.lone O atom and forms a new reaction.

• ClO + O --- Cl + O2.ClO + O --- Cl + O2.

• Cl is back to it’s original state and is now Cl is back to it’s original state and is now free to break down another O3 molecule. free to break down another O3 molecule.

How Long will this Cl atom last How Long will this Cl atom last on this repeating cycle?on this repeating cycle?

• Through these simple reactions, a simple Cl or Through these simple reactions, a simple Cl or Br atom can destroy thousands of O3 molecules Br atom can destroy thousands of O3 molecules like we just looked at. It can continue until it like we just looked at. It can continue until it gets back down to the troposphere. gets back down to the troposphere.

• Here that same Cl atom from earlier can bond Here that same Cl atom from earlier can bond with an H atom to form HCl and finally remove it with an H atom to form HCl and finally remove it from it’s destructive cycle. from it’s destructive cycle.

• However it can take years for this to make the However it can take years for this to make the transition from Stratosphere to troposphere. transition from Stratosphere to troposphere. And while it’s falling it’s doing it’s damage. And while it’s falling it’s doing it’s damage.

Why Care?Why Care? Well…Well…

Gross? Isn’t it!Gross? Isn’t it!

• That was a picture of a victim of skin That was a picture of a victim of skin cancer. Increased exposure of UV-b cancer. Increased exposure of UV-b rays can lead to more causes of skin rays can lead to more causes of skin cancer, cataracts, and impaired cancer, cataracts, and impaired immune system. immune system.

Not just damaging to us.Not just damaging to us.

• More UV-b rays also will damage these:More UV-b rays also will damage these:

Simple Soybean plantsSimple Soybean plants

• Soybean plants are very sensitive to Soybean plants are very sensitive to UV-b light and will cause them to UV-b light and will cause them to yield much less of a crop. yield much less of a crop.

Fish Too.Fish Too.

• Phytoplankton is a tiny Phytoplankton is a tiny plant that is plant that is instrumental in the instrumental in the marine food chain. marine food chain. Many parts of the world Many parts of the world rely on fishing as a rely on fishing as a main source of food. If main source of food. If you damage the you damage the beginning of the food beginning of the food chain, there won’t be as chain, there won’t be as many fish in the end of many fish in the end of the links.the links.

What is being done and what What is being done and what we can do.we can do.

The Environmental Protection Agency (EPA) has The Environmental Protection Agency (EPA) has a long term plan to reduce and eventually a long term plan to reduce and eventually phase out these chemicals containing CFC’s phase out these chemicals containing CFC’s that cause the Ozone to decay. that cause the Ozone to decay.

Regulations have been established which Regulations have been established which require labels on Ozone depleting substances require labels on Ozone depleting substances and the EPA is also prohibiting non-essential and the EPA is also prohibiting non-essential Ozone depleting products.Ozone depleting products.

What about You?What about You?

• Only use maintenance people that are EPA Only use maintenance people that are EPA certified (referring to recovery of certified (referring to recovery of refrigerant, or Freon) to work on your refrigerant, or Freon) to work on your vehicles, refrigerators, and air vehicles, refrigerators, and air conditioners.conditioners.

• Check these items regularly for leaks.Check these items regularly for leaks.• Repair leaks before refilling them with Repair leaks before refilling them with

more refrigerants. more refrigerants. • Dispose of this equipment to local agents Dispose of this equipment to local agents

that are EPA certified.that are EPA certified.

• The Ozone will heal itself. But that is The Ozone will heal itself. But that is a long and slow process. Not in any a long and slow process. Not in any of our lifetimes in fact! All we can do of our lifetimes in fact! All we can do is not advance the damage further. It is not advance the damage further. It will eventually recover. will eventually recover.